1. Technical Field of the Invention
This invention is related to liquid filters and housings for such filters.
2. State of the Prior Art
Liquid filters are used to remove impurities and contaminants from liquids in many applications. In the bio-science and pharmaceutical industries, including biopharmaceutical research and manufacturing (sometimes referred to individually and collectively as “bio-pharmaceutical”), liquid filters are used at various stages of the manufacturing and purification processes to remove contaminants and impurities, including, for example, bio-contaminants, from the process product streams. Filter elements or cartridges with a variety of porosities made with a variety of materials are available for particular applications and filtering needs.
For very high purity applications, for example, final filtering to remove bio-contaminants from biopharmaceutical products, a liquid filter with a base configuration known in the bio-pharmaceutical industry as “code 7” is often specified and used. Code 7 filters are generally characterized by a base that comprises a tubular end piece with O-ring seals and fastening ears or flanges for insertion into a filter housing cavity for bayonet-style attachment, i.e., longitudinal insertion into position and then angular twist or rotation for securing in place.
Such filters remain securely in place with leak-proof seals around the filter base to keep upstream, unfiltered liquid separated from downstream, filtered liquid during stream processing so that only liquid that has passed through the filter medium gets to the downstream side of the filter. However, in many high purity, bio-pharmaceutical systems, the filter cartridges have to be changed often, for example, between each batch process, and the act of changing the filter cartridges results in both potential contamination and waste due to residual, unfiltered, liquid product in the filter housing around the base of the filter cartridge that either drops into the downstream piping or is lost or discarded when the filter cartridge is removed from the housing. While the actual volume of such residual, unfiltered liquid is small, it is enough to cause undesirable contamination in piping and materials downstream from the filter, and it is very valuable at final or near final filter stages, so discarding such valuable material is expensive, especially when repeated after each process batch and for numerous filters in a final filter rack. The cumulative effect of such contamination and/or waste over a period of time is a significant enough problem in the bio-pharmaceutical industry that processors and filter equipment manufacturers have been trying for some time to find a cost-effective solution.